Simple admission control for IP based networks

ABSTRACT

A simple admission control mechanism for IP based networks is provided. The decision on whether a new flow is accepted is based on the link load information on the paths from the source to destination. The new flow is accepted when the link load is less than a threshold. When at least one of the links on all of the available paths is larger than the acceptable threshold, access is denied to the flow. More than one threshold level may be used. Under the multiple threshold scenario, the traffic may be divided into different classes. The admission control mechanism helps to ensure a network that is not heavily congested.

FIELD OF THE INVENTION

The present invention relates to IP networks, and more particularly toan admission control mechanism for IP networks.

BACKGROUND OF THE INVENTION

The development of mobile communication devices and mobile networks hasadvanced at a rapid rate. At first, analog mobile networks enabled voicecommunication and simple paging features. Later, digital mobile networksprovided more advanced features for voice and data communication, suchas encryption, caller identification and short message service (SMS)text messages. More recently, third generation (3G) mobile IP networktechnology is being developed to enable users to easily access contentrich media, information and entertainment with mobile devices.

As mobile devices and mobile networks have advanced, and more data hasbecome available to the users, the demand on the networks has continuedto increase. The increase in demand can cause a network to becomeheavily congested.

One way that has been used to attempt to alleviate congestion on anetwork is to add more bandwidth. This approach, however, has manydrawbacks. Adding more bandwidth is expensive and does not ensure that anetwork will not become congested. Eventually, all of the availablebandwidth will be utilized from the increased demand.

What is needed is a way to simply determine when a new flow should beaccepted into the network in order to avoid congestion. It is withrespect to these considerations and others that the present inventionhas been made.

SUMMARY OF THE INVENTION

The present invention is directed at addressing the above-mentionedshortcomings, disadvantages and problems, and will be understood byreading and studying the following specification.

According to one aspect of the invention, a simple admission controlmechanism is directed at determining when a new flow is accepted into anIP based network.

According to yet another aspect of the invention, the decision whetherto accept a new flow is based on the path congestion for the availablepaths from the source of the new flow to the destination of the newflow. Each link load within the paths is calculated to determine pathcongestion. The link load may be real time load for real time traffic,total load for other traffic, and the like. The link load may be anysubset of the total load that is based on the number of bytes dequeuedfrom certain DiffServ router output queues for any traffic class. Forexample, real time load for Expedited Forwarding (EF) traffic, which ismapped to highest priority queue, may be considered to be congested whenthe threshold is larger than 0.8*link bandwidth. Other trafficthresholds may be set at higher thresholds, e.g. threshold=0.95*linkbandwidth.

When all of the paths are congested, the new flow is not accepted. Whenat least one of the paths is not congested, the new flow is accepted.

According to yet another aspect of the invention, the link load isdetermined by an exponential averaging equation. A configurableweighting factor may be set depending on how fast the operator desiresto react to changes in link loads at each node within the network. Ameasurement period factor may be set for the period the link load ismeasured.

According to still yet another aspect of the invention, the new flow isaccepted when the link load is below a predetermined threshold. Severaldifferent thresholds may be configured. For example, a differentthreshold may be used for different classes of service.

According to a further aspect of the invention, the link loads may bemonitored by a dedicated network element, such as a bandwidth broker, orby individual network nodes, such as routers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary mobile IP network in which the inventionmay operate;

FIG. 2 shows a schematic diagram that illustrates an exemplary systemoverview in which local area networks and a wide area network areinterconnected by routers;

FIG. 3 is a schematic diagram that shows an exemplary bandwidth brokerthat is operative to process information relating to the link loads onthe network;

FIG. 4 illustrates an overview of a simple admission control process;

FIG. 5 shows an exemplary equation for representing link load;

FIG. 6 shows a process for a simple admission mechanism for an IP basednetwork; and

FIG. 7 illustrates a simple admission control utilizing a dedicatednetwork element, in accordance with aspects of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following detailed description of exemplary embodiments of theinvention, reference is made to the accompanied drawings, which form apart hereof, and which is shown by way of illustration, specificexemplary embodiments of which the invention may be practiced. Eachembodiment is described in sufficient detail to enable those skilled inthe art to practice the invention, and it is to be understood that otherembodiments may be utilized, and other changes may be made, withoutdeparting from the spirit or scope of the present invention. Thefollowing detailed description is, therefore, not to be taken in alimiting sense, and the scope of the present invention is defined onlyby the appended claims.

Throughout the specification and claims, the following terms take themeanings explicitly associated herein, unless the context clearlydictates otherwise. The term “node” refers to a network element, such asa router, that monitors a load for a link within a path. The term “linkload” refers to the load associated with the node. The term “bandwidthbroker” refers to a dedicated network element that knows the topologyand link loads associated with the network. The term “flow” means a flowof packets. The term support node refers to both “GGSN” and “SGSN”nodes. The term “user” refers to any person or customer such as abusiness or organization that employs a mobile device to communicate oraccess resources over a mobile network. The term “operator” refers toany technician or organization that maintains or services an IP basednetwork. The term “identifier” includes an MSISDN number, an IP address,or any other information that relates to the location or identity of theuser. Referring to the drawings, like numbers indicate like partsthroughout the views. Additionally, a reference to the singular includesa reference to the plural unless otherwise stated or is inconsistentwith the disclosure herein.

Illustrative Operating Environment

With reference to FIG. 1, an exemplary mobile IP network in which theinvention may operate is illustrated. As shown in the figure, mobile IPnetwork 100 includes mobile station (MS) 105, radio access network (RAN)110, SGSN 115, core network 120, routers 125 _(A-F), optional bandwidthbroker (BB) 300, GGSNs 135 _(A-B), data network 140, and data network145.

The connections and operation for mobile IP network 100 will now bedescribed. MS 105 is coupled to radio access network (RAN) 110.Generally, MS 105 may include any device capable of connecting to awireless network such as radio access network 110. Such devices includecellular telephones, smart phones, pagers, radio frequency (RF) devices,infrared (IR) devices, integrated devices combining one or more of thepreceding devices, and the like. MS 105 may also include other devicesthat have a wireless interface such as Personal Digital Assistants(PDAs), handheld computers, personal computers, multiprocessor systems,microprocessor-based or programmable consumer electronics, network PCs,wearable computers, and the like.

Radio Access Network (RAN) 110 manages the radio resources and providesthe user with a mechanism to access core network 120. Radio accessnetwork 110 transports information to and from devices capable ofwireless communication, such as MS 105. Radio access network 110 mayinclude both wireless and wired components. For example, radio accessnetwork 110 may include a cellular tower that is linked to a wiredtelephone network. Typically, the cellular tower carries communicationto and from cell phones, pagers, and other wireless devices, and thewired telephone network carries communication to regular phones,long-distance communication links, and the like. As shown in the figure,RAN 110 includes routers 125 _(A-C). According to one embodiment of theinvention, routers 125 _(A-C) may calculate their own link loads as wellas process link loads relating to other nodes on the network. Therouters may send a warning message to other routers within the networkwhen its link load exceeds a configurable threshold. When there is atleast one link load within each available path from a source to adestination for a new flow that is above the configurable threshold, thenew flow attempting to enter the network is rejected. Alternatively, abandwidth broker, or some other dedicated network element, may be usedto process information relating to the link loads of the nodes withinthe network. Briefly described, BB 300 may be used to monitor and aid incarrying out the simple admission control for IP based networks.According to this particular embodiment, each router informs BB 300 ofits link load and receives information relating to the link loads forthe other nodes within the network.

Some nodes may be General Packet Radio Service (GPRS) nodes. Forexample, Serving GPRS Support Node (SGSN) 115 may send and receive datafrom mobile stations, such as MS 105, over RAN 110. SGSN 115 alsomaintains location information relating to MS 105. SGSN 115 communicatesbetween MS 105 and Gateway GPRS Support Node (GGSN)s 135 _(A-B) throughcore network 120. According to one embodiment of the invention, BB 300communicates with RAN 110 and core network 120.

Core network 120 is an IP packet based backbone network that includesrouters, such as routers 125 _(D-F), to connect the support nodes in thenetwork. Routers are intermediary devices on a communications networkthat expedite message delivery. On a single network linking manycomputers through a mesh of possible connections, a router receivestransmitted messages and forwards them to their correct destinationsover available routes. Routers may be a simple computing device or acomplex computing device. For example, a router may be a computerincluding memory, processors, and network interface units.

GGSNs 135 _(A-B) are coupled to core network 120 through routers 125_(A-C) and act as wireless gateways to data networks, such as network140 and network 145. Networks 140 and 145 may be the public Internet ora private data network. GGSNs 135 _(A-B) allow MS 105 to access network140 and network 145.

Bandwidth broker (BB) 300 is coupled to RAN 110 and core network 120through communication mediums. BB 300 may be programmed by an operatorwith instructions to manage the admission control of new flows formobile IP network 100. More specifically, the operator may generateconfigurable thresholds and rules to help ensure a network free fromcongestion. BB 300 may receive link loads from the routers within thenetwork, and in response to the received link loads, generate and sendinformation relating to the link loads for the nodes on the network tothe routers. For example, the information may be the link loads for allof the other routers within the network. The information may also beconfiguration rules for the routers. BB 300 is an optional element. Thenodes within the network may be used to carry out the simple admissioncontrol mechanism.

The operator may set threshold levels to determine whether or not toaccept a new flow based on different service classes for a particularuser or group of users. As mentioned above, the routers, or a dedicatednetwork element, such as BB 300, may be used for this purpose. Forexample, conversational traffic from user group A may be carried with anExpedited Forwarding (EF) class would have one threshold level, whereasconversational traffic from user group B carried with an AssuredForwarding (AF) class would have a different service level. The specificuser of MS 105 may be differentiated into one of these user groups bythe user Mobile Station Integrated Services Digital Network (MSISDN)number that is known to both the SGSN and the GGSN support nodes.

Furthermore, computers, and other related electronic devices may beconnected to network 140 and network 145. The public Internet itself maybe formed from a vast number of such interconnected networks, computers,and routers. Mobile IP network 100 may include many more components thanthose shown in FIG. 1. However, the components shown are sufficient todisclose an illustrative embodiment for practicing the presentinvention.

The media used to transmit information in the communication links asdescribed above illustrate one type of computer-readable media, namelycommunication media. Generally, computer-readable media includes anymedia that can be accessed by a computing device. Communication mediatypically embodies computer-readable instructions, data structures,program modules, or other data in a modulated data signal such as acarrier wave or other transport mechanism and includes any informationdelivery media. The term “modulated data signal” means a signal that hasone or more of its characteristics set or changed in such a manner as toencode information in the signal. By way of example, communication mediaincludes wired media such as twisted pair, coaxial cable, fiber optics,wave guides, and other wired media and wireless media such as acoustic,RF, infrared, and other wireless media.

FIG. 2 shows another exemplary system in which the invention operates inwhich a number of local area networks (“LANs”) 220 _(a-d) and wide areanetwork (“WAN”) 230 interconnected by routers 210. On an interconnectedset of LANs—including those based on differing architectures andprotocols—, a router acts as a link between LANs, enabling messages tobe sent from one to another.

Communication links within LANs typically include twisted wire pair,fiber optics, or coaxial cable, while communication links betweennetworks may utilize analog telephone lines, full or fractionaldedicated digital lines including T1, T2, T3, and T4, IntegratedServices Digital Networks (ISDNs), Digital Subscriber Lines (DSLs),wireless links, or other communications links. Furthermore, computers,such as remote computer 240, and other related electronic devices can beremotely connected to either LANs 220 _(a-d) or WAN 230 via a modem andtemporary telephone link. The number of WANs, LANs, and routers in FIG.2 may be increased or decreased without departing from the spirit orscope of this invention. As such, the Internet itself may be formed froma vast number of such interconnected networks, computers, and routersand that an embodiment of the invention could be practiced over theInternet without departing from the spirit and scope of the invention.

FIG. 3 is a schematic diagram that shows an exemplary bandwidth brokerthat is operative to process information relating to the link loads onthe network. Accordingly, BB 300 may receive and transmit data relatingto the simple admission control mechanism. For instance, BB 300 maytransmit link load data and receive link load data from the componentson the IP network.

BB 300 may include many more components than those shown in FIG. 3.However, the components shown are sufficient to disclose an illustrativeembodiment for practicing the present invention. As shown in FIG. 3, BB300 is connected to RAN 110 and core network 120, or othercommunications network, via network interface unit 310. Networkinterface unit 310 includes the necessary circuitry for connecting BB300 to core network 120, and is constructed for use with variouscommunication protocols including the COPS protocol that runs on top ofTCP. Other communications protocols may be used, including, for example,UDP protocols. Typically, network interface unit 310 is a card containedwithin BB 300.

BB 300 also includes processing unit 312, optional video display adapter314, and a mass memory, all connected via bus 322. The mass memorygenerally includes RAM 316, ROM 332, and one or more permanent massstorage devices, such as hard disk drive 328, a tape drive,CD-ROM/DVD-ROM drive 326, and/or a floppy disk drive. The mass memorystores operating system 320 for controlling the operation of BB 300.This component may comprise a general purpose operating system 320 as isknown to those of ordinary skill in the art, such as UNIX, LINUX™, orMicrosoft WINDOWS NT®. Basic input/output system (“BIOS”) 318 is alsoprovided for controlling the low-level operation of BB 300.

The mass memory as described above illustrates another type ofcomputer-readable media, namely computer storage media. Computer storagemedia may include volatile and nonvolatile, removable and non-removablemedia implemented in any method or technology for storage ofinformation, such as computer readable instructions, data structures,program modules or other data. Examples of computer storage mediainclude RAM, ROM, EEPROM, flash memory or other memory technology,CD-ROM, digital versatile disks (DVD) or other optical storage, magneticcassettes, magnetic tape, magnetic disk storage or other magneticstorage devices, or any other medium which can be used to store thedesired information and which can be accessed by a computing device.

The mass memory also stores program code and data for simple admissioncontrol program 330 (See Figures and Related discussion below), andprograms 334. Simple admission control program 330 includes computerexecutable instructions which, when executed by BB 300, help inexecuting the simple admission control mechanism across the IP basednetwork. BB 300 may include a JAVA virtual machine, an HTTP handlerapplication for receiving and handing HTTP requests, JAVA applets fortransmission to a WWW browser executing on a client computer, an IPsechandler, a Transport Layer Security (TLS) handler and an HTTPS handlerapplication for handling secure connections. Either the IPsec handler orthe TLS handler may be used to provide security protection for the COPSprotocol. HTTPS handler application may be used for communication withexternal security applications (not shown), to send and receive privateinformation in a secure fashion.

BB 300 may also comprise an input/output interface 324 for communicatingwith external devices, such as a mouse, keyboard, scanner, or otherinput devices not shown in FIG. 3. Likewise, BB 300 may further compriseadditional mass storage facilities such as CD-ROM/DVD-ROM drive 326 andhard disk drive 328. Hard disk drive 328 is utilized by BB 300 to store,among other things, application programs, databases, and program dataused by simple admission control program 330. For example, link loads,topology of the network, user databases, relational databases, and thelike, may be stored.

Simple Admission Control for IP Based Networks

FIG. 4 illustrates an overview of a simple admission control process400, in accordance with aspects of the invention. After a start block,the process moves to block 410 at which point the process monitors fornew flows attempting to enter the network. Transitioning to decisionblock 415, a determination is made as to whether a new flow has arrived.When there is not a new flow, the process returns to block 410 tocontinue monitoring for new flows. When there is a new flow, the processmoves to block 420 at which point the congestion of the path isdetermined. According to one embodiment of the invention, the linkcongestion for all of the possible paths from the source to destinationof the flow is determined. For each path from the source to destination,a link load for each link within the path is calculated. A link iscongested when the link load is larger than a configurable threshold.For example, the link may be congested when the link load is larger thana threshold of 90%. Other thresholds may be chosen. Stepping to decisionblock 425, a decision is made as to whether all of the paths the flowmay use are congested. When all of the paths are congested, the processsteps to block 430 where the new flow is discarded. In other words, thenew flow is not accepted by the IP based network. When at least one ofthe paths is not congested, the process steps to block 435, at whichpoint the new flow is accepted. Transitioning to block 440, the processchooses the path for the new flow. According to one embodiment of theinvention, the least congested path is chosen. The path may be chosenusing some other method. For example, the path may be chosen on numberof hops, shortest distance, or some other parameter. The path may alsobe chosen based on a class of service. The process then advances to anend block and returns to processing other actions.

FIG. 5 shows an exemplary equation for representing link load. Theequation:link load_(i)=(1−w)*link load_(i−1) +w*(8*bytes per period_(i)/(p*linkcapacity))is used to calculate link load 510 according to one embodiment of theinvention. Weighting parameter “w” 520 is configurable, and according toone embodiment of the invention, is set at 0.5. Weighting parameter “w”520 relates to how much weight previous link load values are given inthe equation. In other words, weighting parameter “w” 520 is setdepending on how fast the operator desires the link load value to reactto the changes in link loads. Measurement period parameter “p” 530 isthe period of time the load for the node is measured. According to oneembodiment of the invention, measurement period parameter “p” 530 is 500milliseconds. Other measurement period parameters may be used. Linkcapacity 540 is the capacity of the particular link being measured.According to one embodiment of the invention, link capacity is measuredin bits per second (bps).

The link load may be real time load for real time traffic, total loadfor other traffic, and the like. The link load may be any subset of thetotal load that is based on the number of bytes dequeued from certainDiffServ router output queues for any traffic class. For example, realtime load for Expedited Forwarding (EF) traffic, which is mapped tohighest priority queue, may be considered to be congested when the realtime load is larger than real time threshold (e.g., 0.8*link bandwidth).Other traffic thresholds may be set at higher thresholds, e.g. totalthreshold=0.95*link bandwidth.

FIG. 6 shows a process for a simple admission mechanism 600 for an IPbased network. After a start block, the process moves to decision block610 where a determination is made as to whether a timer has expired.According to one embodiment of the invention, the link load for eachnode is calculated at predetermined periods. For example, the timer maybe set at 500 milliseconds. When the timer has not expired, the processwaits for the timer to expire. When the timer has expired, the processmoves to block 620 at which point the link load is calculated. Accordingto one embodiment of the invention, the link load is calculated usingthe exponential averaging equation illustrated in FIG. 5.

Transitioning to decision block 630, a determination is made as towhether the link load exceeds a predetermined threshold. The link andany path that the link is within is congested when the link load isabove the predetermined threshold. The predetermined threshold may beset to many different values. For instance, the threshold may be set at90% of link capacity. Additionally, more than one threshold may be usedto determine when a link is congested. For example, a differentthreshold may be chosen for each different service class. When thethreshold is exceeded, the process steps to decision block 635, at whichpoint a determination is made as to whether a congestion bit is set toindicate that the link is not congested. According to one embodiment ofthe invention, a bit within the node is set to a value of one when thelink is congested and is set to zero when the link is not congested.

According to another embodiment of the invention, a dedicated networkelement, such as a bandwidth broker, may maintain the congestion statesof the links (See FIG. 7 and related discussion). Other indicators maybe used to represent that a link is congested. At block 635, when thecongestion bit is set to not congested, the process transitions to block640 where a warning message is sent to the other nodes within thenetwork indicating that a particular link is congested. Stepping toblock 645, the process sets the congestion bit within the node toindicate that its link is congested. Stepping to block 665, the timer isset. When the congestion bit has already been set to congested, theprocess moves to block 665 to set the timer. The nodes do not need to beinformed that the link is congested when the congestion bit waspreviously set, as all nodes have already been notified that the link iscongested.

When the threshold load has not been exceeded the process steps todecision block 650 where a determination is made as to whether thecongestion bit has been set to congested. When the congestion bit isset, the process transitions to block 655, at which point a link OKmessage is sent to all hosts. This message informs the other nodes onthe network that the link may be used again. At this point in time, thelink is no longer congested and may accept new flows. Stepping to block660, the congestion bit is set to indicate that the node is notcongested. Moving to block 665, the timer is set. The process isrepeated according to a timed period. The process advances to an endblock and returns to processing other actions.

FIG. 7 illustrates a simple admission control utilizing a dedicatednetwork element, in accordance with aspects of the present invention.After a start block, the process moves to block 710, at which point linkload information is received from a node on the network. Moving to block720, the path information is updated in response to the received linkload. Transitioning to block 730, load information may be sent to thenode. The load information may contain many different types of data. Theload information may contain the link loads for each node within thenetwork. The load information may also include routing rules for thenodes.

The above specification, examples and data provide a completedescription of the manufacture and use of the composition of theinvention. Since many embodiments of the invention can be made withoutdeparting from the spirit and scope of the invention, the inventionresides in the claims hereinafter appended.

1. A method comprising: determining when a flow arrives; for each of aplurality of links within a path for the flow, receiving a messageindicating whether or not the link is congested; determining from theplurality of received messages whether or not the path is congested; andaccepting the flow if the path is determined not to be congested,wherein accepting the flow comprises one of sending a packet over one ofthe plurality of links that was received on another of the plurality oflinks or sending a bandwidth broker message to each node through whichone of the plurality of links passes, where the bandwidth broker messagecomprises one of link loads for the plurality of links or configurationrules for the flow.
 2. The method of claim 1, wherein determiningwhether or not the path is congested further comprises receiving in eachmessage a link load, and comparing each received link load to apredetermined threshold to determine whether or not the path iscongested.
 3. The method of claim 1, wherein the network comprises aradio access network.
 4. The method of claim 1, wherein each of themessages indicating whether or not the link is congested is received:upon at least one of the conditions: a change to a congestion status ofthe link; and expiration of a timer.
 5. The method of claim 1, whereineach of the messages indicate congestion by a link load that isrepresented by an exponential averaging equation.
 6. The method of claim1, executed by a bandwidth broker.
 7. The method of claim 5, wherein theexponential averaging equation is:link load=(1−w)*link load_(i-1) +w*(8*bytes per period_(i)/(p*linkcapacity)), wherein link capacity is bits per second, w is a weightingparameter and p is a measurement period parameter over a time period forwhich the load is measured.
 8. The method of claim 1, whereindetermining from the received plurality of messages whether the at leastone path is congested comprises reading from each received message acongestion bit indicating the link is congested or not congested.
 9. Themethod of claim 1, wherein a new message is received for each link nomore frequently than when that link changes between congested and notcongested, and expiration of a timer kept by a node through which thatlink passes.
 10. The method of claim 1, wherein determining when a flowarrives further comprises determining a service class of the flow; andfurther wherein determining whether or not the path is congested isspecific for the service class.
 11. The method of claim 1, wherein thereare a plurality of paths for the flow, wherein a message is receivedfrom each link within each of the plurality of paths indicating whetheror not the link is congested and determining whether or not the path iscongested is for each of the plurality of paths, and wherein acceptingthe flow comprises choosing a least congested path from among theplurality of paths.
 12. A computer readable storage medium storingcomputer executable instructions when executed by a computer perform thefollowing: for each of a plurality of links within a path through anetwork, receiving a message from a node through which the link passesthat indicates whether or not the link is congested; determining fromthe plurality of messages whether or not the path is congested; andaccepting a new flow that is satisfied by the path if the at path isdetermined not to be congested, wherein accepting the new flow comprisesone of sending over one of the plurality of links a packet that wasreceived on another of the plurality of links or sending a bandwidthbroker message to each of the nodes through which one of the pluralityof links passes, where the bandwidth broker message comprises one oflink loads for the plurality of links or configuration rules for the newflow.
 13. The computer-readable storage medium of claim 12, whereindetermining from the plurality of messages whether or not path iscongested further comprises receiving in each message a link load, andcomparing the link load to a predetermined threshold.
 14. Thecomputer-readable storage medium of claim 12, wherein determining fromthe plurality of messages whether or not the path is congested furthercomprises calculating a link load from each of the messages.
 15. Thecomputer-readable storage medium of claim 14, wherein the link load iscomputed as:link load_(i)=(1−w)*link load_(i-1) +w*(8*bytes per period_(i)/(p*linkcapacity)), wherein link capacity is bits per second, w is a weightingparameter and p is a measurement period parameter over a time period forwhich the load is measured.
 16. The computer-readable storage medium ofclaim 12, wherein the network comprises a radio access network.
 17. Thecomputer-readable storage medium of claim 12, wherein the computerreadable storage medium and processor are disposed in a bandwidthbroker.
 18. The computer-readable storage medium of claim 12, whereinthe instructions further comprise determining a service class of the newflow; and further wherein determining whether or not the at least onepath is congested is specific for the service class.
 19. Thecomputer-readable storage medium of claim 12, wherein the instructionsoperate for a plurality of paths through the network and each link iswithin at least one of the plurality of paths, and wherein accepting theflow comprises choosing a path from among the plurality of paths basedon a parameter selected from the group: least congested; number of hops;and shortest distance.
 20. A system comprising: nodes arranged along anavailable path through an internet protocol based network, each nodecomprising a network interface unit arranged to communicate across thenetwork a message indicating whether or not a link through the node iscongested or not congested; and a bandwidth broker that is configured toprocess information relating to each of the messages received from thenodes, wherein the bandwidth broker comprises: a network interface unitarranged to communicate with the nodes; a processor; and an admissioncontrol program embodied on a computer-readable storage medium executingunder the control of an operating system and operative to performactions, including: receiving from each of the nodes the congested orthe not-congested message; and for a new flow between a source anddestination coupled by the available path, accepting the new flow if themessage from each node along the available path is a not-congestedmessage, wherein accepting the new flow comprises sending from thenetwork interface unit a bandwidth broker message to each of the nodes,where the bandwidth broker message comprises one of link loads for thenodes or configuration rules for the new flow.
 21. The system of claim20, wherein the internet protocol-based network comprises a radio accessnetwork.
 22. The system of claim 20, wherein each node further comprisesa processor configured to calculate a link load, and wherein the messageis based on a comparison of the link load to a threshold.
 23. The systemof claim 22, wherein the link load is calculated according to:link load_(i)=(1−w)*link load_(i-1) +w*(8*bytes per period_(i)/(p*linkcapacity)), where w is a weighting parameter and p is a measurementperiod parameter over a time period for which the load is measured. 24.The system of claim 20, wherein the instructions further comprise:calculating at the bandwidth broker a link load from each of thereceived messages.
 25. An apparatus comprising: means for determiningwhen a flow arrives; means for determining, from a plurality ofmessages, each message received from a node associated with a linkwithin an available path for the flow, whether the available path iscongested; and means for accepting the flow when the available path isdetermined not to be congested, wherein accepting the flow comprises oneof sending from a sending means over one of the links a packet that wasreceived on another of the links or sending a bandwidth broker messageto each of the nodes, where the bandwidth broker message comprises oneof link loads for the links or configuration rules for the new flow. 26.The apparatus of claim 25, wherein: the means for determining when aflow arrives comprises a processor coupled to a network interface unit;the means for determining whether the available path is congested andthe means for accepting the flow comprises the processor; and thesending means comprises the network interface unit.
 27. An apparatuscomprising: a processor and a network interface that are configured todetermine when a flow arrives; the processor configured to determinefrom a plurality of messages, each message received from a nodeassociated with a link within an available path for the flow, whetherthe available path is congested; and the network interface configured toaccept the flow when the available path is determined not to becongested by one of sending over one of the links a packet that wasreceived on another of the links or sending a bandwidth broker messageto each of the nodes, where the bandwidth broker message comprises oneof link loads for the links or configuration rules for the new flow. 28.The apparatus of claim 27 comprising a bandwidth broker.
 29. Theapparatus of claim 27, wherein each of the plurality of messagescomprises a link load, and the processor is configured to determinewhether the available path is congested by comparing the link load ofeach of the plurality of messages to a
 30. The apparatus of claim 29,wherein the link load is represented by an exponential averagingequation.
 31. The apparatus of claim 30, wherein the exponentialaveraging equation is:link 1oad_(i)=(1−w)*link load₁₋₁ +w*(8*bytes per period_(i)/(p*linkcapacity)), wherein link capacity is bits per second, w is a weightingparameter and p is a measurement period parameter over a time period forwhich the load is measured.